feat: documentation website using Vitepress

Adds documentation website using https://vitepress.dev.

Some decisions are questionable, for example creation of a symbolic link
for the README in the `docs/`. I wanted to preserve the ability to read
docs using Github. Maybe not needed.

Another issue, is the page outline for the `NixOS` chapter is too
narrow.

But should serve as a scaffold/basis for doing it properly.

package.json

@@ -10,7 +10,10 @@
 		"dev": "HEADPLANE_LOAD_ENV_OVERRIDES=true HEADPLANE_CONFIG_PATH=./config.example.yaml react-router dev",
 		"start": "node build/server/index.js",
 		"typecheck": "tsc",
-		"test": "vitest run"
+		"test": "vitest run",
+		"docs:dev": "vitepress dev docs",
+		"docs:build": "vitepress build docs",
+		"docs:preview": "vitepress preview docs"
 	},
 	"dependencies": {
 		"@dnd-kit/core": "^6.3.1",
@@ -67,6 +70,7 @@
 		"@types/node": "^22.15.17",
 		"@types/websocket": "^1.0.10",
 		"drizzle-kit": "^0.31.1",
+		"js-yaml": "^4.1.0",
 		"lefthook": "^1.11.13",
 		"postcss": "^8.5.4",
 		"react-router-dom": "^7.6.1",
@@ -77,7 +81,7 @@
 		"typescript": "^5.8.3",
 		"vite": "^6.3.5",
 		"vite-tsconfig-paths": "^5.1.4",
-		"js-yaml": "^4.1.0",
+		"vitepress": "^1.6.4",
 		"vitest": "^3.1.3"
 	},
 	"packageManager": "pnpm@10.4.0",
@@ -90,8 +94,14 @@
 			"react-router-hono-server": "patches/react-router-hono-server.patch"
 		},
 		"supportedArchitectures": {
-			"os": ["current", "linux"],
-			"cpu": ["x64", "arm64"]
+			"os": [
+				"current",
+				"linux"
+			],
+			"cpu": [
+				"x64",
+				"arm64"
+			]
 		},
 		"onlyBuiltDependencies": [
 			"@biomejs/biome",